This application claims the benefit of International Application No. PCT/IB00/00469 which was published under PCT Article 21(2) in English.
THIS Invention relates to a supplementary torsion spring assembly for a vehicle coil suspension spring.
A number of different methods exist for supplementing the coil springs of a vehicle so that the suspension acts more effectively when carrying a full load or when towing trailers or caravans. These range from the rudimentary, in the form of tennis bails which are located between adjacent turns of the coil spring, to various relatively sophisticated pneumatic and/or hydraulic arrangements which aim to prevent normal deflection of the spring. Tennis balls and similar elastomeric inserts tend to lose their elasticity with time, and are non-adjustable. Pneumatic and hydraulic arrangements, or even special heavy duty coil springs, can prove to be expensive.
According to the invention there is provided a supplementary torsion spring assembly for supplementing the compressive resistance of a coil spring, the spring assembly including a torsion spring having a central torsion-producing portion and first and second outwardly splayed arms extending from opposite ends of the torsion-producing portion and first and second corresponding arm mounting means for mounting the arms to non-adjacent turns of the coil spring.
In a preferred form of the invention, the supplementary torsion spring assembly includes intermediate mounting means for mounting the torsion-producing portion to an intermediate turn of the coil spring between the non-adjacent turns, with the first and second arms being mountable to the first and second arm mounting means in a sliding fit.
Preferably, the intermediate mounting means is integral with the torsion-producing portion and includes a central bight portion which is sized and shaped to engage the intermediate turn of the coil spring.
Conveniently, the bight portion terminates in a pair of torsion-producing turns from which the first and second arms extend.
In one form of the invention, the turns are approximate half turns.
Alternatively, the turns are approximate 3/2n turns, where n=1, 3 or 5.
Typically, the central bight portion is a C-shaped bight portion having a narrowed opening which is adapted to be widened by forcing free ends of the first and second arms towards one another, the C-shaped bight portion being sized and shaped to engage the intermediate turn of the coil spring in a compression fit by introducing the intermediate turn through the widened opening.
Preferably, each of the first and second arm mounting means include a mounting block having an aperture formed therein for slidably receiving the free ends of the first and second arms.
Conveniently, each of the mounting blocks include a spring-receiving opening for receiving the non-adjacent turn of the coil spring in a snap or friction fit.
In one form of the invention, the supplementary torsion spring assembly includes a pair of torsion springs and coupling means for coupling the pair of torsion springs together in a side-by-side relationship.
Conveniently, the coupling means include the first and second arm mounting means which are arranged simultaneously to mount the pairs of first and second arms to the non-adjacent turns of the coil spring.
Preferably, the coupling means further include a pair of cheek plates and at least one plate securing bolt for sandwiching the pair of torsion springs between the cheek plates.
Typically, the coil spring is a vehicle suspension coil spring.
The invention extends to a method of fitting a supplementary torsion spring assembly to a coil spring of a vehicle, the spring assembly including a central torsion spring having a torsion-producing portion, first and second outwardly splayed arms extending from opposite ends of the torsion-producing portion, and first and second corresponding arm mounting means for mounting the arms to non-adjacent turns of the coil spring, the method including the steps of:
mounting the torsion-producing portion to an intermediate turn of the coil spring between the non-adjacent turns; and
fitting the first and second arms to the non-adjacent turns of the coil spring via the mounting means.
Preferably, the torsion-producing portion includes a central, substantially C-shaped bight portion shaped and sized to engage the intermediate turn, the method including the step of forcing the first and second arms towards one another to expand or define a narrowed opening in the C-shaped portion which is sufficient to receive the intermediate turn.